Disinfection of the potable water supply onboard transportation vehicles is needed to guarantee the water quality that is uploaded to the vehicle tanks, particularly from international water sources. Water systems on aircraft especially, are complicated systems that usually include a tank with manifolds plumbing, and a pressurization system to deliver the water to the points of use. There are a number of reasons why clean and/or potable water is needed on-board a vehicle, such as an aircraft. For example, clean water is needed for handwashing in the lavatory sinks, and potable water is needed for use to brew coffee or deliver hot tea to passengers.
The issue of water quality, and in particular, of potable water quality, on passenger transportation vehicles and equipment, such as aircraft, trains, boats and ships, and the like is becoming more of a concern to regulatory authorities. This is particularly true in the United States with respect to the potable water supplies contained aboard commercial aircraft. Regulatory standards have been enacted that require water on board passenger vehicles to be disinfected according to certain standards. Passenger airlines must thus implement appropriate aircraft water disinfection protocols.
U.S. Pat. No. 4,871,452 to Kohler, et al., entitled “On-Board Water Supply,” discloses equipment for purifying waste water from galleys, sinks, and toilets of aircraft. Waste water from these areas discharges to a tank, after which it passes through a mechanical filter, a bed of active carbon, ozone and osmotic stages, and a disinfection stage involving addition of chlorine and irradiation with ultraviolet (“UV”) light. Thereafter, the water is made available to aircraft passengers for certain uses.
U.S. Pat. No. 6,143,185 to Tracy, et al. entitled “Treatment System for Aircraft Toilet Waster Water” discloses alternate systems for decontaminating waste water from aircraft toilets, sinks, and galleys. They too include a mechanical particulate filter, activated carbon, and a source of UV light. Alternatively, according to the Tracy patent, the waste water may be exposed to microwaves or treated with chlorine or iodine. A sensor may be used to measure “the level of clarity of the treated water as an indication of its purity” and restrict opening of a control valve until acceptable clarity levels are obtained.
However, these systems and methods are primarily directed at purifying wastewater removed from the aircraft. Airlines and other passenger transport vehicle companies must also ensure that the potable water (i.e., drinkable water) aboard the aircraft is fit for human consumption by employing appropriate disinfection protocols. But disinfection upon upload and periodic disinfection sampling does not always adequately address the issue of contamination introduced in uploaded water, which is of particular concern for aircraft flying to and from, and being serviced in, non-industrialized areas. In addition, air must be introduced into the water storage and dispensing system on the aircraft in order to maintain pressurization, as well as to drain the system during routine servicing. This air can introduce pathogens that can multiply and cause unsanitary conditions and unacceptable water quality in the intervals between samplings or disinfection procedures. In effect, because the water storage and dispensing system is routinely exposed to the outside environment, potable water quality cannot always be ensured without some form of additional treatment.
Ultraviolet treatment eliminates bacteria, viruses, spores and mold in the water and works similar to the way that strong sunlight can permanently purify water by making biological impurities inactive. Ultraviolet lamps are generally designed to destroy the links in these micro-organisms' DNA so that they are de-activated and cannot reproduce. The crucial hydrogen bonds that link the DNA chain together rupture when exposed to light between the wavelengths of about 220 nm to about 310 nm. As discussed above, UV water treatment has been used in many water purification circumstances, including on-board passenger transport vehicles such as aircraft, in order to treat and purify the water circulating on-board.
There are currently a number of water treatment solutions being employed and/or studied for use on-board aircraft. For example, one way that water can be treated is via UV mercury lamps. These lamps deliver an ultraviolet light to the water in the system and have been found beneficial because the treatment does not change the taste or odor of the water, it kills bacteria, viruses and protozoan, it is compact and easy to use, and it can prevent biofilm if the system is kept clean. However, one of the disadvantages of mercury UV lamps for water treatment is that they require a medium to high electrical demand, which means that when used on-board a vehicle such as an aircraft, they pull electrical power from the aircraft engines and/or an auxiliary power unit (APU). Increased usage of aircraft power from the engines results in higher fuel consumption and costs. Other disadvantages are that UV mercury lamps require cleaning and new lamps annually, and if a mercury lamp is broken, there exists a chance for mercury contamination of the water to be treated. Additionally, UV lamps take a while to power on if not in constant use.
Another method of water treatment has been to use UV light with photo-catalytic agents. In addition to the above benefits, this treatment may require less power than the UV lamp alone and it may be used with other UV sources, although it may impede or otherwise slow the flow of water through a reaction chamber. Some of the materials related to the use of photo-catalytic agents are EP2047870, which uses mercury lamps and photo-catalyst-coated chamber walls. These walls incorporate a sequence of cone shapes protruding from the cylinder interior of the chamber walls. The cones are coated with a photo-catalyst (normally titanium-dioxide at which point the reactive species of hydroxyl and superoxide are created to kill pathogens), and the cone shapes are intended to slow the flow of the water (essentially creating turbulence) and increase the surface area of the reactions where oxidative species are created. Another related attempt is described in U.S. Pat. No. 6,238,631, which uses a mesh-type arrangement where the water becomes trapped while moving and is in contact with the catalysts and a spiral, in which the water is forced to rotate around a blade-like arrangement in order to exit the tube. Other related photo-catalyst treatment documents are U.S. Pat. Nos. 5,933,702; 5,501,801; 6,558,639; 7,988,923; and 7,927,554.
A further method of water treatment that has been explored is the use of UV LED (light emitting diode) light for water treatment. In addition to the mercury lamp benefits, the use of UV LED light also has the advantage of being able to use a wider UV band with multiple LED wavelengths, can offer a high power output with less power consumption than UV lamps, UV LEDs have greater longevity, power up quickly without requiring a delay time built into the system for the UV light source to reach its optimum UV energy output, and do not contain mercury. Some companies have been manufacturing UV lamps and LED systems for water sanitation and disinfection, but none of the available systems are designed for use on-board a transportation vehicle or an aircraft. For example, some systems are being developed and investigated for use in treating city-scale water by companies such as Trojan Technologies and Sterilite. However, most of these proposed technologies use outdated UV lamp designs as opposed to LEDs. Aquionics is a company that provides a UV LED system called the UV-Pearl™. This system provides a separate unit, which can be integrated into a water line system or used as a stand-alone unit. However, this system is not an inline system that is incorporated into the actual water supply line. Instead, it is a stand-alone unit that is incorporated into a break in the line, and thus does not become a part of the actual water line itself. It is not truly “in line” with the water supply line.
For existing aircraft, retrofitting a UV disinfection device can be costly, space prohibitive, and require extra wiring (power and operating status), extra plumbing, and the resulting systems may be unable to operate at the proper level of initial designed performance. Other incarnations have used UV purification units at aircraft water upload on the ground, but that too must be a fully-integrated device at the system level. There is also a need to further disinfect the water once it has been circulating in the aircraft water pipe system for a period of time, as the water may also need to be treated on an on-going basis, particularly as it is being delivered to the point of use.
Therefore, a current need exists for a UV LED system for use in a vehicle or aircraft environment that is space efficient, energy efficient, accessible, and that is located in close proximity to a power supply and a water-system plumbing. It is also desirable to provide a system that can be added to existing systems, as opposed to having to replace the entire plumbing system on the vehicle.